Denitrogenation of petroleum with potassium hydroxide of low water content



United States Patent 3,260,666 DENITROGENATION OF PETROLEUM WITHPOTASSIUM HYDROXIDE OF LOW WATER CONTENT Richard A. Flinn, Emmaus, andOlaf A. Larson, Oakmont, Pa., assignors to Gulf Research & DevelopmentCompany, Pittsburgh, Pa., a corporation of Delaware No Drawing. FiledOct. 27, 1964, Ser. No. 406,876 2 Claims. (Cl. 208-254) This applicationis a continuation-in-part of our copending application Serial Number160,339, filed December 18, 1961, now abandoned.

This invention pertains to the removal of nitrogen-containing compoundsfrom petroleum fractions and in particular to the removal of nitrogencompounds from petroleum fractions which are to be subsequentlyhydrocracked.

It is known that nitrogen compounds occur in many petroleum fractions.These nitrogen compounds have various deleterious eliects. For instance,these nitrogenous materials have a poisoning effect on crackingcatalysts and the removal of nitrogen-containing substances fromcatalytic cracking feed stocks has been quite thoroughly investigated.Also these nitrogenous materials have a poisoning etfect onhydrocracking catalysts and there has been fairly extensiveinvestigation of these effects and of methods for removal of nitrogencompounds from hydrocracking feed stocks. The problems involved in suchremoval have not been completely overcome. This is particularly truewith respect to hydrocrackin-g procedures for medium or heavy feedstocks. These higher boiling feeds contain higher boiling nitrogencompounds which are exceedingly diffioult to remove; at least theirremoval to a sufii-cient degree to avoid poisoning of the hydrocrackingcatalyst has been a difficult problem. It is of course known that thesepoisonous materials can be removed by hydrogenation treatment. Howeverthe thorough-going removal required for hy-drocraoking feed stocks hasnecessitated relatively high pressures of above about 2000 psi. andrelatively low space velocities.

This invention has for its object to provide improved procedure forseparation of nitrogen-containing contaminants from petroleum fractions.Another object is to provide improved hydrocrackin-g procedure. Otherobjects will appear hereinafter.

It has now been discovered that these and other objects may be achievedby treating a petroleum fraction, which contains nitrogen compounds,with solid potassium hydroxide which has a water content of 0-10% atelevated temperatures and separating the petroleum fraction \from .thepotassium hydroxide and nitrogen reaction products. It has beendiscovered that potassium hydroxide, with less than water content, andespecially with about 5% water content, is extraordinarily effective inremoving nitrogenous compounds from petroleum fractions. It has beenfurther discovered that the process which includes subjecting apetroleum fraction which contains nitrogenous compoundsto be removed totreatment with potassiurn hydroxide which contains 0-10% water,preferably 5% water, at elevated temperature; separating the petroleumfraction from the solid potassium hydroxide and solid precipitatednitrogenous material formed by reaction with the potassium hydroxide;and then hydrogenating the so arated petroleum fraction, is a new andeifective method for eliminating the most dilficult to removenitrogenous compounds which remain. The hydrogenation treatment iscarried out in the presence of a hydrogenation catalyst at elevatedtemperature and at moderate pressures. It results in hydrogenation ofnitrogen compounds which remain in the petroleum fraction after thepotassium hydroxide treatment. In the event that the petroleum frac-3,260,666 Patented July 12, 1966 tion treated as above is to behydrocracked, the so treated fraction is then subjected tohydrocracking. This procedure results in thorough removal of nitrogencompounds to such an extent that the activity of the hydrocrackin-gcatalyst is not deleteriously affected.

The feed stocks to our process may be any hydrocarbon mixture, which issubstantially \free of asphaltic material, having a boiling point aboveabout 250 C., which contains above about 25 p.p.m. of nitrogen. The feedstock must be substantially free of asphaltic materials since suchsubstances have a harmful effect on the catalyst used in the second orhydrogenation stage of our process (and in the third stage when ahydrocracking operation follows the nitrogen removal). Our invention isof particular value for the treatment of furnace oil, especiallycatalytic furnace oil. Light and heavy catalytic cycle stocks anddeasphalted residuum are examples of other feed stocks that can beadvantageously employed. Also our invention is applicable to solventextracts of various petroleum fractions. LP or instance, our process isapplicable to a sulfur dioxide extract of a catalytic cycle stock. Alsoour invention is applicable to products produced by pyrolysis ofcarbonaceous material such as creosote oil or shale oil.

The solid potassium hydroxide used in our process must contain from 010%water. 'It is preferred that the Water content be about 5%. Solidpotassium hydroxide containing above 10% water is not satisfactory inthat it does not result in a thorough removal of the most difficultlyremovable nitrogen compounds. Therefore when this commercial product isused substantial amounts of these most difficultly removable nitrogencompounds remain in the petroleum fraction. The subsequent moderatepressure hydrogen treatment Will not adequately remove these difiicultlyremovable nitrogenous substances and therefore the preparation of asatisfactory final product for hydrocracking or for other purposes doesnot result. There is a sharp increase in the capacity for nitrogenremoval when the water content of the solid potassium hydroxide is lessthan 10%. The most efiective level is about 5 There is some lessening ofdenitrogenative capacity as water is removed further. The solid KOH isemployed in an amount of between about 0.1 and 15 percent and preferablybetween about 2 and 5 percent by weight of the petroleum fraction. Anelevated temperature is employed during the treatment with solidpotassium hydroxide. A temperature above about 200 F. but below thecracking temperature of the oil, and preferably between about 250 and350 F. may be employed. The treatment with the solid potassium hydroxideis continued for a period of between about 10 minutes and 4 hours.Actually a longer time than 4 hours may be used but is accompanied by noadvantage since the beneficial results of the treatment are fullyobtained with the shorter periods mentioned. A time of treatment ofbetween about one-half and 1 hour is usually most advantageous. Thecontacting of the petroleum fraction with the solid potassium hydroxidemay be accomplished using any method which will result in thoroughcontact between a solid and a liquid. For instance, the contacting maybe accomplished in batch fashion by simply stirring the two reactantstogether in a container. A much more satisfactory procedure is to flowthe petroleum fraction through a stationary mass of particles, pelletsor beads of the solid potassium hydroxide. If desired, the two reactantscan be passed countercurrently to each other. After the treatment withthe potassium hydroxide the petroleum fraction is filtered, distilled,settled or otherwise treated to remove any solid potassium hydroxidewhich might be suspended therein and to remove nitrogenous reactionproducts. These reaction products are usually solid materials and can beadvantageously removed by filtering or decanting. If there are traces ofice potassium hydroxide left in the feed it is advantageous to removethem by Washing with water. The potassium hydroxide cannot be reused inthe process unless it is first regenerated at elevated temperature tothermally decompose the nitrogenous salts formed. It can be reactivatedby calcining at a temperature above about 800 F. After calcining, watermay be added as desired.

The hydrogen treatment to remove the remaining nitrogen compounds isadvantageously carried out at a temperature between about 550 and 750 F.and preferably between about 600 and 700 F. The pressure isadvantageously maintained between about 200 and 1500 p.s.i.g. Therequired degree of nitrogen removal usually can be obtained utilizingpressures of between about 400 and 1000 p.s.i.g. A space velocity ofbetween about 0.5 and and preferably between about 1 and 6 is generallyused. The hydrogen recycle rate is maintained between about 1000 and20,000 s.c.f./bbl. and preferably between about 2000 and 10,000s.c.f./bbl. The catalyst employed in this first stage is advantageouslya mixture of nickel and tungsten oxides or sulfides, of nickel andmolybdenum oxides or sulfides. The most effective catalyst of this groupis a mixture of nickel and tungsten oxides and a catalyst having aparticularly high activity for nitrogen removal is one containing amixture of 16 parts nickel and 16 parts tungsten in the form of theoxides. While We have found these catalysts to be unusually effectivefor nitrogen removal, we can in general employ metal oxides or sulfidesof metals of Group VI left-hand column of the Periodic System or irongroup oxides or sulfides or mixtures thereof. These catalysts aredeposited upon solid porous carriers such as alumina, kieselguhr orsteam deactivated silica-alumina cracking catalyst. As a matter of fact,since the nitrogen deactivates the cracking activity, these catalystsmay be deposited upon a conventional cracking catalyst. Thus thecracking activity of the carrier is very quickly lost due to thepoisoning efiect of the nitrogen in the feed stock and the poisonedcarrier then serves as a satisfactory porous non-cracking carrier.

The product from the above hydrogenation may be used for any purpose inwhich a low nitrogen feed is advantageous. Thus it may be subjected to ahydrocracking operation. This is accomplished by contacting thedenitrogenated feed with hydrogen in the presence of a hydrogenationcatalyst deposited upon a silicious carrier having cracking activity. Atemperature of between about 450 and 800 F. and preferably between 550and 750 F. is used, and a pressure of between about 500 and 2000 andpreferably between about 700 and 1500 p.s.i.g. is employed. A spacevelocity of between about 0.1 and 10 and preferably between about 0.5and 3 will in general be found satisfactory. The hydrogen recycle ratemay be between about 2000 and 20,000 and preferably 6000 and 10,000s.c.f./bbl. The hydrogenating component of the hydrocracking catalystmay be a noble metal or an iron group metal. Also an oxide or sulfide ofmetals of Group VI left-hand column may be used, alone or in combinationwith a noble metal or an oxide or sulfide of an iron group metal.Examples of satisfactory catalysts are tungsten oxide or sulfide,molybdenum oxide or sulfide nickel, nickel oxide or nickel sulfide,platinum, palladium and mixtures of Group VI left-hand column oxides orsulfides with iron group metal oxides or sulfides such as nickeltungstate and cobalt molybdate. The carrier for the hydrogenatingcomponent may be any known silicious cracking catalyst such as asilica-alumina cracking catalyst. These cracking catalysts may lEllSOcontain activators such as are commonly used in cracking catalysts, forinstance magnesium oxide or strontium oxide. Also these catalysts may beactivated with halides such as fluorine.

EXAMPLE I A commercial grade of potassium hydroxide (nominallycontaining water) was calcined at 1000 F. for 16 hours to render itcompletely anhydrous. It Was then placed under a nitrogen atmosphere toprevent any water absorption. Five batches of nine grams each of theanhydrous potassium hydroxide were weighed out under a nitrogen blanket.Calculated amounts of water were added so that five lots of potassiumhydroxide were available, one being anhydrous and the others containing5%, 10%, 15% and 25% water, respectively.

A fluid catalytically cracked furnace oil which contained 360 p.p.m. ofnitrogen in the form of nitrogenous compounds was selected for treatmentwith each of the potassium hydroxide samples. The complete inspectiondata on this charge stock are contained in Table I. Each of thepreviously prepared samples of potassium hydroxide was added to 300grams of the furnace oil. The mixtures were heated rapidly to 300 F.with constant agitation. The temperature was maintained at 300 F. forfour hours. The oil was then filtered and washed twice with water. Itwas then analyzed for nitrogen. Each analysis was run in duplicate. Theresults are summarized in Table II.

DIDNITRIFICATION OF FCC FURNACE OIL IVI'IH POTASSIUM I-IYDROXIDENitrogen Nitrogen Nitrogen Water in Potassium Hydroxide AnalysisAnalysis Analysis (p.p.m.) (p.p.m.) Average EXAMPLE II The same furnaceoil was treated in a manner identical with that in Example I except thatonly four samples of potassium hydroxide were tested. One was ananhydrous sample. Water concentration, in the others, was 5%, 10% and 15The potassium hydroxide samples were also prepared identically withthose in Example I.

After the oil product was filtered and washed, it was analyzed fornitrogen. The results of this testing are contained in column 1 of TableIII.

The oil was then subjected to a hydrogenation treatment over a sulfidednickel-cobalt-molybdenum catalyst at a pressure of 1000 p.s.i.g. and at650 F. The liquid hourly space velocity was 5 and the hydrogen recyclerate, 4000 standard cubic feet per barrel of feed. The oil was againtested after the hydrogenation for nitrogen content. These results arein column 2 of Table III. The oil that had been treated with anhydrouspotassium hydroxide was not tested after hydrogenation but it isestimated that about 12 p.p.m. of nitrogen would remain. This estimateis based On the other data in Table III.

3,260,666 5 6 Table III 2. A process for removing nitrogen compoundsfrom a petroleum fraction which comprises contacting said fraction withpotassium hydroxide containing about 5% N Leve1 After water andseparating the potassium hydroxide and nitro- Hydrogenation (P.P.m.) 5gen reaction products.

HYD BO GENATION OF KOH-TREATED FCC FURNACE OIL N-Level Before Water inKOH Used to Hydrogenation (P-P- Treat Sample (percent) References Citedby the Examiner 240 49. 220 14. UNITED STATES PATENTS 80 Less than 5.185 No test (estimated 12). 2,704,758 3/1955 Wetzel 208-254 10 2,719,1109/1955 Rampino 20s 254 2 768 121 10/1956 Dcnton et a1 208-254 What Weclaim 1s: 1. A process for removing nitrogen compounds from 33 apetroleum fraction which comprises contacting said fraction withpotassium hydroxide containing less than 10% 15 DELBERT GANTZ, PrimaryExaminer water and separating the potassium hydroxide and nitrogenreaction products S. P. JONES, Asszstant Examiner.

1. A PROCESS FOR REMOVING MITROGEN COMPOUNDS FROM A PETROLEUM FRACTIONWHICH COMPRISES CONTACTING SAID FRACTION WITH POTASSIUM HYDROXIDECONTAINING LESS THAN 10% WATER AND SEPARATING THE POTASSIUM HYDROXIDEAND NITROGEN REACTION PRODUCTS.